Aspects of Polarization in Optical Fiber Transmission

Abstract

The increasing demand for bandwidth is driving towards the deployment of large capacity transmission systems. Systems based on 10 Gb/s channel rates are being deployed and the plans for channel rates as high as 40 Gb/s are in offing. The paper considers polarization effects as an important limiting parameter for high speed communication networks like SONET and STM. This limitation is estimated in terms of polarization mode dispersion (PMD). PMD is caused by asymmetry in the fiber geometry and by localized stress throughout the waveguide (birefringence). Representation of polarization in optical fibers has been presented. Various polarization handling methods have been discussed. As polarization mode dispersion represents a major impairment for high bit rate systems producing pulse broadening and distortion leading to performance degradation, measuring and then minimizing polarization mode dispersion is becoming increasingly important in high performance fiber optic systems. Since optical transmission systems are usually made of several components each contributing the total PMD effect on the transmission system, even small PMD values (10–100 fs) of the type found in fiber or optical components must be determined to guarantee the performance of the transmission link. General PMD compensation/equalization and measurement techniques have been reviewed in the paper.